Telecommunications – Carrier wave repeater or relay system – Portable or mobile repeater
Reexamination Certificate
2000-05-30
2003-12-23
Maung, Nay (Department: 2684)
Telecommunications
Carrier wave repeater or relay system
Portable or mobile repeater
C455S517000, C455S575900, C701S050000
Reexamination Certificate
active
06668157
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to data sharing equipment for mobile stations, which comprises a plurality of mobile stations moving along runways and a monitor station for monitoring the plurality of mobile stations, and more particularly to data sharing equipment for mobile stations for efficiently delivering data shared among the mobile stations.
2. Description of the Related Art
Equipment for sharing data among a plurality of mobile units is known described in Japanese Patent Application Laid-Open No. 4-319991. Such equipment provides an operation schedule of each mobile unit, and states of roads and traffic to a destination of the mobile unit from central control equipment to the mobile unit. Thus, the mobile bodies can be guided by such information.
But, when the central control equipment and the mobile unit communicate mutually, this equipment has to transmit a large volume of data every time data is needed, resulting in increasing a load upon a communication line.
In addition, there is also used widely a system which provides a plurality of work machines at mines and construction sites with guidance on works by means of positioning equipment such as GPS and a total station. These work machines share data, which indicates the present landform, target landform, work schedule and work progress, to proceed the work. When the number of work machines is not many, each of data may be transmitted directly from a central station to the work machines. But, when the number of work machines is increased, data must be transmitted to the plurality of work machines, and a load upon the communication line is increased accordingly, making it hard to transmit individually. And, since the data transmission is started when data is required, the work machine has to stop working while the data is transmitted and received. Thus, there is a wasted standby time.
To decrease the communication load, broadcasting may be used to transmit to all the vehicles, but since the central station does not receive any response from the receiving side, it cannot be confirmed whether the communications are completed properly or not.
Such a problem can be solved by transmitting and receiving data by a communication method which requires an acknowledgment of reception (ACK). This communication method includes point-to-point communication and multicasting.
The point-to-point communication requires the central station to communicate with each of the plurality of work machines and takes much time to do so. And, a load on the communication line is increased because the central station receives an acknowledgment of reception from the work machines.
The multicasting can transmit data from the central station to the plurality of work machines in the same way as the broadcasting, but a load upon the communication line is increased because the central station receives an acknowledgment of reception from the plurality of work machines in the same way as the point-to-point communication.
Besides, a plurality of work machines working together may have inconsistencies in data among the plurality of work machines, resulting in causing a trouble. For example, it is assumed that track A is moved along course a and loaded by loading machine B. When the next truck C is to be loaded, the operator of the loading machine B presumes that the truck C runs the same course a as the truck A did and operates the loading machine B to stand by. But, it may happen that the truck C approaches through a different course a
1
, and the loading machine B and the truck C may collide mutually.
In such a case, it is possible to use the multicasting so to transmit simultaneously to all the vehicles (work machines) and to separately receive an acknowledgment of reception from all the vehicles. But, a load on the communication line is increased because of the acknowledgments of reception from the plurality of vehicles.
It is also necessary to transmit data again when there is no acknowledgment of reception from a vehicle which does not need the data at all because it is far away.
Furthermore, by selectively transmitting to vehicles which may need data, an acknowledgment of reception may be received from those vehicles. But, it is hard to predict which vehicles need data, and if such prediction is not correct, there is a danger of causing an accident that such vehicle colloid each other.
SUMMARY OF THE INVENTION
Under the circumstances as described above, it is an object of the invention to provide data sharing equipment for mobile stations which suppresses a load on a communication line for data communications between a monitor station and mobile stations and to reduce a standby time required for data communications of the mobile stations.
To achieve the aforethe object, a first aspect of the invention is directed to data sharing equipment for mobile stations, comprising a plurality of mobile stations moving along runways and a monitor station for monitoring the plurality of mobile stations, wherein:
the plurality of mobile stations and the monitor station are provided with communication means for transmitting and receiving data to and from other stations;
the mobile stations are provided with storage means for storing data transmitted from other stations, and the monitor station or at least one of the plurality of mobile stations are provided with imparting means for giving identification information to predetermined data for identifying the predetermined data;
predetermined instructions are given to the mobile station with identification information given by the imparting means; and
the mobile station instructed by the identification information, when data corresponding to the identification information is not stored in its storage means, transmits a demand for transmission of data corresponding to the identification information to the monitor station or other mobile station through the communication means.
A second aspect of the invention is directed to the data sharing equipment for mobile stations according to the first aspect of the invention, wherein:
the monitor station is provided with data storage means for storing data as a reference and identification information imparting means for giving identification information for identifying data to the data stored in the data storage means, and transmits the data stored in the data storage means and the identification information given to the data to the plurality of mobile stations by broadcasting;
the monitor station or any one of the plurality of mobile stations transmits predetermined instructions to other stations by the identification information; and
the mobile station instructed by the identification information, when data corresponding to the instructed identification information is not stored in the own storage means, transmits a demand for transmission of data corresponding to the identification information to the monitor station or other mobile stations.
A third aspect of the invention is directed to the data sharing equipment for mobile stations according to the first aspect of the invention, wherein:
the monitor station is provided with data storage means for storing data as a reference and identification information imparting means for giving identification information for identifying data to the data stored in the data storage means, and transmits latest identification information given to latest data stored in the data storage means by the identification information imparting means to the plurality of mobile stations by periodically broadcasting through the communication means; and
when the latest data corresponding to the latest identification information from the monitor station is not stored in the storage means and judges that the latest data is required, the mobile station transmits a demand for transmission of the latest data to the monitor station or other mobile stations through the communication means.
A fourth aspect of the invention is directed to the data shearing equipment for mobile stations according to the first,
Kageyama Masato
Ozaki Tomonori
Takeda Koji
Lele Tanmay
Varndell & Varndell PLLC
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